1. Field of the Invention
This invention relates to a zoom lens and an electronic imaging apparatus using the zoom lens, and in particular, to an electronic imaging apparatus, including a video camera or a digital camera, in which a slim design regarding a depth direction is attained.
2. Description of Related Art
Recently, special attention has been devoted to digital cameras (electronic cameras) as the next generation cameras that are an alternative to cameras for silver halide 35 mm films (135 formats). The digital cameras have come to have many categories in a wide range from a high-function type for business use to a popular portable type.
The greatest obstacle to a reduction in depth of a camera is the thickness of an optical system, notably extending from the most object-side surface of a zoom lens system to an imaging surface.
The main current of a slim design technique for a camera body in recent years is to adopt a so-called collapsible lens barrel in which the optical system protrudes from the camera body in photography, but when the camera is carried, it is incorporated in the camera body. Examples of optical systems, each having the possibility that the collapsible lens barrel is adopted and the slim design can be effectively attained, are set forth in References 1-3 described below. Each of these optical systems includes, in order from the object side, a first lens unit with negative refracting power and a second lens unit with positive refracting power, which are moved together when the magnification of the optical system is changed.                Reference 1: Japanese Patent Kokai No. Hei 10-213745        Reference 2: Japanese Patent Kokai No. 2002-72095        Reference 3: Japanese Patent Kokai No. 2002-90624        Reference 4: Japanese Patent Kokai No. 2004-4533        Reference 5: Japanese Patent Kokai No. 2004-264343        Reference 6: Japanese Patent Kokai No. 2004-163477        
Zoom optical systems in which the optical path (the optical axis) of the optical system can easily be bent by a reflection optical element such as a mirror are set forth in References 4-6. In particular, Reference 5 discloses the addition of an image processing step of electrically processing image data obtained by an electronic image sensor to change the shape thereof.
However, there are particular demands for a zoom ratio of at least 3, a further decrease in depth, a reduction of the overall length of the optical system or housing dimensions, and a further improvement on compactness of the entire camera. In addition, there is a demand that, in a collapsible type, the compact design of the entire body should be attained by reducing the diameter of a front lens to make the lens barrel compact.